November 24, 2003
Monday - 12:15 am

Last year, Ketchikan had several otter deaths that were attributed to the parasite Toxoplasma. Toxoplasma uses cats as an intermediate host, meaning that cats carry it without any signs Several people asked me whether runoff contaminated with cat feces

Sophia Photo by MC Kauffman

posed a threat to people using area beaches.

It's a smart question, because Toxo is excreted in the feces, but the short answer to the smart question is that human infections by Toxo are usually asymptomatic. The only people who need to watch out for Toxo are pregnant women, because Toxo can be transmitted transplacentally to the embryo. If the infection occurs in the first trimester, fetal death and/or abortion occurs. If the transmission occurs in the last trimester, then neurological and visual abnormalities are the most common result.

There are two ways to come in contact with Toxo. The first is eating the undercooked meat of something else that's been infected with Toxo - and almost anything vertebrate can be infected - or by eating the Toxo life stage called the sporulated oocyst. Since oocysts are formed in cat intestines, and excreted in cat poop, those in contact with cats are at greatest risk of contracting the disease.

Oocysts don't sporulate til they've spent one to three days in the optimum conditions of heat and humidity, so cleaning cat boxes daily and throwing the feces away daily, greatly decreases the odds of infection. What this means is that pregnant women should either: 1) wear gloves when they change the cat boxes or 2) wash their hands after changing the cat box or... Best idea 3) have someone else change the cat box.

This doesn't solve the entire problem, but it minimizes it. The unfortunate part is that oocysts can survive in the environment up to a year, and there's no guarantee that they're all ending up in the cat box. The recommendation is that pregnant women avoid contact with cats as much as they can. Most experts agree that women who get infected before they get pregnant are not at risk for transplacental transmission.

Finally, the answer to the question of the otter deaths, and risk from freshwater runoff is - I dunno. Like I said earlier, it takes a certain set of conditions for oocytes to sporulate, and what those conditions are, you'd have to ask a bacteriologist. Since otters are dying of Toxo, there must be some risk to them. But to humans? Only to pregnant women, as the rest of us tend toward asymptomatic infections, and only if the conditions are right for sporulation of the oocysts.

To put it in perspective a little, the cycle that produces oocysts is self-limiting. A test of a humane society showed that 50% of all the cats had been infected with Toxo, but only 1% of the cats were shedding oocysts. It's not all cats all the time, just infected cats for a small period of time.

There are plenty of other things, much more dangerous, and more likely to affect you, that would make better candidates for causing insomnia. I guess I wouldn't lose any sleep over this one.

 
franimaldoc@sitnews.org

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